Telephone system



May 22, 1923. 1,456,172

G. A. YANOCHOWSKI TELEPHONE SYSTEM Filed Jan. 16, 1919 @miim/ Patented ay 22, 1923 GEORGE YANOCHOWSKI, OF CHICAGO, ILLINOIS, ASSIGNGR TO KELLOGG STCH-' BOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINQIS, A CORPORATION OF ILLL.

TELEPHONE SYSTEM.

Application filed January 16, 1919. erial.No. 271,386.

To. all whom it hwy/concern: v Be it known that I, Gnonon A. YarrocnoWsKI, a citizen of the United States of America, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

In general my invention relates to calldistributing systems and is more particularly directed to improved apparatus and circuits for the connecting links used in such systems.

A feature of my invention is the provision of means whereby after a subscriber has operated his individual switch mechanism to extend a connection to an idle operators cir I cult and the operator has extended the connection in the direction of the called subscriber, the replacing of the receiver at the calling substation and .the removal thereof again operates to automatically flash a supervisory signal of the operators connecting circuit to notify the operator that a recall is desired. It the calling .subscriber should replace his receiver before the operator has extended the connection in the direction of the called subscribers line, the subscribers individual switch mechanism will be released irom connection with the operators connecting circuit when he replaces his receiver.

Another feature of my invention is the provision of a .testless operators circuit whereby the operator after receiving the number of the wanted line connects the calling plug ofthe link circuit directly to a jack of the wanted line without first test ing to determine whether or not the called nection of the calling subscribe'rs line to an idle link circuit' I also provide means :tor preventing a connection from being extended to an operators position if the operator at said position is engaged in answering another call. A recall key is provided to associate the operators set with the cord circuit and to operate a group busy relay.

These and other features of my invention will be more fully described in the ensuing specification and pointed out in the appended claims. For a more complete understanding of my invention, reference may be had to the accompanying drawing which diagrammatically illustrates my invention.

Referring now more in general to my invention as illustrated, it comprises a substation A connected by line conductors L to multiple jacks J and to an individual line switch B at the central oflice, there bein one such individual switch B associate with each of the substations. 'lhe switches B have access to a lurality of connecting circuits or link circuits Cf The link circuits C terminate in plugs in difl'erent operators positions and are distributed and grouped in any desirable manner to efficiently handle the trallic. At the right of the sheet of drawings 1 have illustrated a called substation E connected by line conductors L to apparatus similar to that connected to the substation vA. In general the system op erates as follows:

Generoi operation of system.

The subscriber A removes his receiver from the switch hook, which act starts the individual line switch wipers 3, i and 5 stepping around to select an idle cord or link circuit C at an idle operators position,

The selection of anidl'e link circuit G by the line switch B automatically connects the operators set i) to the calling subscribers line and renders the remaining trunks leading to the selected operators position un-- selectable to other individual switches. The operator is then informed by the calling subscriber the number of the wanted line. The operator next inserts the calling plug P into a jack J of the wanted line, and the called subscriber is either rung automati- Mil cally or the' calling subscriber is supplied with a busy signaling current, dependent upon the idle or busy condition of the called line. After the conversation is finished the subscribers restore their respective receivers on the switch hooks, lighting the supervisory lamps, and the operator disconnects the plug P from the jack of the called line. The individual switch B is restored to normal and is now available for use in extend Before proceedinging other connections. with a more detailed description of the c1r cuits, I will refer to the selector switch mechanism of the individual switch B.

Description of apparatus.

The switch referred to in the preceding paragraph in general comprises sets of bank contacts 6, 7 and 8, preferably ten, and cooperating wipers 3, 4 and 5 which are mounted upon a central shaft carrying a ratchet wheel adapted to be driven by the motor magnet MM. Two check pawls are employed, one of the check pawls being normally in engagement wit-h the ratchet and the other being normally out of engagement with the ratchet. For a better understanding'of thecheck pawl arran ement, reference may be had to Patent 310. 1,210,386,

. granted December 26, 1916; The check pawl 40 wheel and thereafter the cut-off relayCO is energized, causing its associated pawl to disengage the ratchet wheel. Thereafter the motor magnet MM advances the wipers over the bank contacts. followed by the de-energization of cut-0E relay CU, but relay LR is maintained energized sothat both pawls are now in engagement withthe ratchet wheel. To release the switch B, line relay LB is tie-energized, thus withdrawing its pawl from engagement with the ratchet, and

thereafter cut-ct? relay ()0 is again energized moving its pawl out of engagement with the ratchet, allowin the wipers to be restored by a suitable coil spring. On the first step, off-normal contacts ON assume their alternate position and are maintained so until the wipers are restored, whereby said contacts Oh are again moved to their normal position. It is understood that vari- 6 ous other types of line switches may be used With the cord circuit of my invention. For exampie, a line switch as shown in my Patent No. 1,314,453, dated August 26, 1919, may be used, or a line switch of the character shown in. my copendin g application 243,292, filed July 5, 1918, maybe used. My invention in this application does not relate to the type of line switch; therefore, I have merely represented a line switchof the prior art in this application. I could have just as well illustrated a line switch of either necessary contact springs and circuit connec-v tions are also switch B.

The connecting or link circuit C terminates at its one end in bank contacts in the individual switches andat its other end in a plug P for use in establishing connection with called subscribers lines via their multiple jacks J. The link circuit C is also provided with an answering supervisory relay AS and a calling supervisory relay CS for assisting in the control of answering supervisory lamp AL and calling supervisory lamp CL. A call initiating lamp CIL is also provided. An operators recall key K is provided as well as automatic ringing apparatus including the necessary interrupters and generators, etc. A pair of test control relays TC and T'C are provided for use in testing the called line as to its idle or busy condition. A group relay GB, common to the operators position, is provided and is energized when a subscribers line is connected to an idle link circuit C at the opcrators position. This relay upon energizing renders all. the remaining idle trunks at the operator s position artificially busy to ali incoming cails until the first connection has been extended to the called subscribefs line. A busy back BB and other necessary apparatus are provided and wili be more fully hereinafter described.

The called substation E and individual switch B are similar to the calling substation A and its individual switch B.

Having described in general the apparatus of my invention, I will now describe in detail the operation of the same.

provided for the individual Operation 0 f system.

Assuming that the subscriber at substatil) ' the busy contact.

from battery through the winding of relay LR, wiper 5, conductor S, normal contact 9 of the cut-off relay CO, conductor 2, through the substation A, conductor 1, normal contact 10 of the cut-o'fi' relay CO and wiper 4 to ground at contact 7. Upon the energization of relay LR an energizlng circuit for the cut-01f relay CO is established from battery through the winding of cutoff relay CO, the normal contactof offnormal contacts ON, to ground at alternate contact 11 of relay LR, energizing the cut-off relay CO. Relay CO therefore closes its alternate contact 12 which establishes an energizing circuit for the motor magnet MM, traced from ungrounded pole of alternating current generator G through the motor magnet MM, alternate contacts 12, 13 to ground. Themotor magnet MM energizes stepping the wipers 3, 4 and 5 around and if the first contacts are busy the motor magnet continues to step the wipers around until an ungrounded test contact 6 is encountered. Upon the first step of the wipers, the off-normal switch ON assumes its alternate position opening the energizing circuit for cut-off relay CO but assuming that the first contact isbusy, another circuit for relay CO is established from battery through the winding of CO, alternate contact 14, conductor 15, alternate contacts 16, 17 of relay LR, conductor 18, wiper 3. contact 6, conductor 19 to ground at another cord selector associated with lVhen the private wiper 3 finds an 'ungrounded contact, relay CO deenergizes interrupting the circuit of the motor magnet MM and rendering the wipers- 3, 4 and 5 inert. Relay LR places a busy' potential upon the sleeves of multiple jacks J. \Vhen the individual switch B has selected an idle cord circuit C, the answering supervisory relay AS of cord circuit C is energized overa circuit traced from battery through the upper winding of said relay AS, through bank contact 7, the wiper 4, out over the calling line, through the calling substation, back over conductor 2 of the calling line, through wiper 5, bank contacts 8 and the lower winding. of the relay AS to ground. l pon energization of relay AS a holding circuit for the line relay LR of the switch B is established extending from batterythrough the windingot' line relay LR. its alternate contacts 16 and 17, private wiper 3. bank contact 6.- resistance 20 and conductor 21 to ground at alternate contact 22 of relay AS. A further result due to the energization of relay AS is the closing of a circuit for the call initiating lamp ClL and slow-acting relay 25 in multiple. The circuit for the call initiating lamp CIL extends from battery through normal contact 26 of relay TC, lamp (ill; and alternate contact 22 to ground The answering supervisory-relays of the idle cord circuits. Relay 25 upon energizing connects the operators set 0 through alternate contacts 30 and 31 and.- throu 'h nornial contacts 32 and 33 of relay Ta, over the talking conductors of thecord circuit C and over the telephone line to the calling substation. The 0 erator is now in conversational circuit wlth the .calling subscriber and is apprised of which cord cir- -c uit the calling subscriber A'has selected by the glowing of the call. initiating lamp- CIL.

The operator now inquires 0? the calling subscriber the number of the called substation desired. If, at this time, the calling subscriber should replace his receiver, the opening up of the circuit of the answering supervisory relay AS 'at the substation would de-energize the same and remove the hold-- ing ground from the private conductor 21, thereby releasing the individual switch B to normal and also releasing the group relay GR and slow-acting relay 25, thus returning all the apparatus to normal. Assuming, however, that the calling subscriber does not replace his receiver, but on the contrary that the operator places the-plug P of the cord circuit Cinto a" multiple jack' J of the called substation E. The connection of the said plug P to the jack .J of the substation E causes the cut-ofi relay C0 of the line switch B to be energized in series with the test control relays TC and TC, providing thatthe substation,

E is idle, over a circuit traced from battery through the winding of relay CO, sleeve contact of jack J and sleeve contact plug P, through the windings of relays TC and TO to ground. The cut-off relay CO energizing removes the control of the switch B from the substation E. The relay TC energizes whether or not the line of the called subscriber isbusy, while the relayTC only energizes when the connection is established with the line of an idle subscriber. The relay TC is provided with a higher resistance winding than the winding TC and energizes whether ornot ground is connected to the multiple jacks J through a resistance. while the relay TC will not energize if a ground potential through a resistance is found upon the test contact of the multiple jacks J. Ground may be placed upon the test contact and jacks either through the relays of the cord circuit con- .nected with a multiple jack, or through the resistance 23 of line switch B if line switch B is used for calling purposes. In case line switch B is used, battery is connected to the sleeve of the multiple jacks J, through contact 23, when the line switch is used for calling urposes, and through the cut-off relay C when it is used for called purposes. Relay TC upon energizing establishes a circuit for relay 35,,extending from battery through the winding of said relay and alternate contact 36 of relay T'C to ground. Relay 35 upon energizing places ground upon private conductor 21 through its alternate contact 37 and extends the talking conductors of the cord circuit through to the line of the called subscriber. lishes an energizing circuit for calling supervisory lamp CL traced from battery through, normal contact 39 of relay CS,

through the filament of said lamp CL, alter-' nate contact 40 of relay TC and alternate contact 41 ofrelay 35 to ground. The relay TC upon energizing also removes the battery connection from group relay GR and lamp CIL by opening its contact 26. Relay GR tie-energizing removes ground from the private bank contacts 6 of the cord circuits associated with this particular operators position. If the calling subscriber should replace his receiver at this time, a circuit for relay 45 would be established traced from battery through alternate cont-act 46 of relay 35, over conductor 47, through the winding of said relay 45, and through normal contact 22 to ground.

Relay 45 energizing locks itself to ground at alternate contact 48 of relay TC and closes 'a circuit for supervisory lamp AL through its alternate contact .49. In this instance, the subscriber A does not release his individual switch B as it is locked up over conductor 21 to ground at alternate contact 37 of relay 35.

A further result due to the energization of relay 35 was the closing of circuit for ringer relay RR, traced from battery through the interrupter I, normal contact 50 of relay CS, winding of said relay RR, normal contact 51 of relay 52 and alternate contact 37 of relay 35 to ground. The relay RR upon energizing connects ringing current from the generator G to the called substation E, through alternate contacts 53 and 54 of relay 35. Through the medium of interrupter I, relay RR is intermittently energized and tie-energized to alternately connect ringing current to the said called line. The removal of the receiver from the called subscribers switch hook closes a path Relay TC upon energizing estab- K for calling supervisory relay (38' extending through normal contacts 56 and 57 of relay RR, alternate contacts 53 and 54 of relay 35, through the plug and jack connections and through the substation E. The relay CS upon energizing opens the energizing circuit of relay RR, opens the circuit of calling supervisory lamp CL at .its normal contact 39, and closes acircuit for relay 52 through its alternate contact 39. Relay 52 upon energizing closes a locking circuit for itself through its alternate contact 55, independent of alternate contact 39 of relay CS, and opens the circuit of relay HR at its contact 51, thereby preventing further applications of ringing current to the called line until the plug P has been removed from the jack of the called line. The subscribers may now carry on a conversation over the heavily marked conductors shown in the drawing including condensers K and The subscribers at substations A and E havlng finished conversation replace their receivers upon their respective switch hooks, opening energizing circuits for the relays AS and CS. Relay AS de-energizing closes a circuit for relay 45 over a path extending from battery through alternate contact 46 of relay 35, winding of said relay 45, and normal contact 22 to ground. The relay 45 upon energizing closes a locking circuit for itself through its alternate contact 60 to ground at alternate contact 48 of relay TC, and also closes a circuit for answering supervisory lamp AL, traced from battery, through the filament of said lamp, alternate contact 49 of relay 45 to ground at normal contact 22 of relay AS. The relay CS deenergizing closes a circuit for calling supervisory lamp CL, traced from battery through normal contact 39 of relay CS, the said lamp CL, alternate contact 40 of relay TC to ground at alternate contact 41 of relay 35. The operator, observing the two lights glowing, knows that the subscribers have re- 1 placed their receivers, and removes the plug from the ack J. This act opens the series circuit of relays TC, T'C and CO. The relay T'C tie-energizing opens the energiz-- ing circuit of relay 35. Relay 35 de-energizing opens the holding circuit for relay LR of the switch B. A further result due to the de-energization of relay 35 is the opening mascara ment with the ratchet on the shaft of switch- B and as LR is de-energized, its pawl is withdrawn from the said ratchet wheel, thereby restoring wipers 3, 4: and 5 to normal. Upon restoration of the wipers,ofinormal contact ON assumes its normal position opening the energizing circuit of relay CO, restoring it and now the switch being at normal, the line of substation A is available for further use. The relays of the cord circuit C all having returned to normal, the link circuit C is now available. for further use.

Assuming that the calling subscriber A had desired to make a recall immediately before the operator had removed the link circuit plug P from the jack of the called subscribers line, the replacing of the receiver at the calling substation operates to ener ize relay 45 and closes a circuit for lamp L. The subse uent removal of the receiver at the substation A again energizes relay AS; thereby connecting interrupter I in circuit withv the supervisory lamp AL over a path extendin from battery through the said lamp A alternate -contact 49 of relay 45,

and alternate contact 62 of relay AS to ground at interrupter I. The interrupter I thus intermittently flashes the supervisor? lamp AL to notify the operator that the cal ing subscriber desires to make a recall. The operator now actuates her'listeningkey K to connect her telephone set 0 across the conductors of the link circuit and'converses with the calling subscriber. The operation of the key K closes an energiz-in' circuit for" rou rela GR thereb ener izm the same find endezing all the idle l ink ircuits' at the operators position busy to incoming calls. The circuit for group relay GR extends from battery through contact 640i ke K and through the winding of said relay G to ground. The operator after inquiring the wants of the calling subscriber removes the plug P from the jack or the called line, if it is a different subscriber that the calling subscriber desires restores her key K to normal and establishes the recall connection as she did the previously described connection.

Assuming now that the line of the called subscriber E was busy when the plu P was connected to the jack J, of the cal ed line,

the rela TC will energize, as before mentioned, ut the relay T'C will fail to energize. The relay TC energizes-over a circuit extending from ground through the winding of sald relay TC, winding of rela; T'C, sleeve contacts of plug P and 'acl: J and through relay CO to battery. attery rupter I".

from conductor 21 permits the rela LR of is to be found upon the sleeve of the jacks J either through the winding of the cut-01f relay CO or through the contacts 23 of the relay LR. The battery potential causes the relay TC in the cord circuit C .to always energize, whether the connected-with called line is busy or idle while the relay T'C only energizes when t e connected-with called line is" idle.--- Thefailure of relay T'C to energize prevents the energization of relay 35, thereby preventing the' application of ringin current to the called subscribers line. he relay TC' energizin opens the energizing circuit for group re ay GR removes batte from the calling lamp CIL, 0 disconnects t e operators set from the link circuit and closes a busy signaling circuit, extending from the busy back BB through normal contact 66 of relay T C, alternate contact 33 of TC to talking conductor 67, 8

and out through the calling substation A'- and back over theother conductor to ground. A rurther result due to the energization of relay TC is the closing of a circuit for calling lamp CfL extendingfrom batte through. normal; contact 39 o--1=elay C through said lamp CL, alternate contact 40 of relay TC and-through normal contact 41 qt relay d5 to ground through the inter- The interrupter I operates to alternately flash the calling supervisory lamp CL to notify the oplerator that the called subscriber is busy. be calling subscriber now replaces his receiver in response to the busy signal and causes the de-energization of'relay AS. .Relay AS de-energizing removesround from the slow-acting relay 25 and 'a so removes ground from the holding conductor 21. T e removal of ground theline switch B to de-energize an restore the line switch B to normal before the slow relay 25 has had time to de-energizeand close its normal contact 69. The closure of normal contact 69places a guarding potential upon the private contact 6 of the individual switches Bto prevent the cord circuit C from being selectedbefore the 0 erator removesthe plug P from the jack of the ca'lled line. This guarding potential extends from ground at alternate contact 48 of relay TC, through normal contact 69 of relay 25 to the said private contact 6. The operator in response to the flashlng of the callin supervisory lamp CL removes the plu from the ad: of the called subscri rs line, there y permitting relay TC to de-energize and restore the apparatus of cover all such changes and modifications as come within the spirit and scope of the appended claims.

What I claim as new and desire to secure by United States Letters Patent, is:

1. A telephone system includin calling and called subscribers lines, a link circuit, an automatic switch for connecting said calling subscribers line and said link circuit, manually controlled means for connecting said link circuit to said called subscribers line, a source of signaling current, a source of busy! current, automatic means responsive to the connection of said link circuit to said called subscribers line to either connect the signalin current to the called'subscribers line or t e bus current to the callin subscribers line ependent upon the i la or busy condition of the called subscribers line, a supervisory lamp for said link circuit, and means for automatically flashlng said supervisory lamp responsive to a single actuation of the switchhook at the calling substation.

2. A telephone system including a calling and a called'subscribers line, a link circuit, an automatic switch for connecting said calling subscribers line to said link circuit, manually controlled means for connecting said link circuit to said called subscribers line, a supervisory signal, a source of busy current, automatic means responsive to the connection of said link circuit to said 'called subscribers line, if said called subscribers line is busy, to connect said busy current to said alling subscribers line, and to intermittently operate the said supervisory! Sig-- nal, a second supervisory lamp and 'substation-controlled means for intermittently closing a circuit through said second superviso lamp to cause the same to intermittently flash to denote a recall.

'3. A telephone system including calling and called subscribers lines, a link circuit, an automatic link selecting switch provided with movable contacts capable of assuming a plurality of selective positions, means including said automatic switch and said link circuit for connecting said lines in conversational circuit, a supervisory signaling device associated with said link circuit, and means associated with the link circuit and controlled by the restoration of the switch hook at one of the connected substations to cause the continuous operation of said supervisory device to furnish a disconnect signal and by the subsequent removal of the receiver to alter the continuous operation of the device and thereafter cause the intermittent operation of the signaling device to furnish a recall signal.

4. A telephone system including a calling and a called subscribers line, a plurality of link circuits, an automatic switch connecting calling subscribers to an intense idle one of said link circuits, an operators circuit for disconnecting said operators set from said link circuit and for restoring said common means, and automatic means for intermittently signaling the subscriber at the called substation.

5. A telephone system including a calling and a called subscribers line, a link circuit provided with a manually-controlled terminal, automatic means including a progressively movable switch for connecting said calling subscribers line to said link circuit, means for said link circuit responsive to such connection for automatically connect-.

ing the operators telephone set to said link circuit, manually controlled means for connecting said link circuit tosaid called subscribers line, and means responsive to such connection for automatically disconnectin said operators telephone set from said link circuit and for automaticall intermittently signaling the called subscri r.

6. A telephone system including a calling and a called subscribers line, a link circuit provided with a manually controlled terminal, automatic means including a progressively'movable switch for connecting said calling telephone line to said link circuit, an operators telephon set, automatic means responsive to such connection for connecting said operators telephone set to said link circuit, automatic testing means for said link circuit responsive to the connection of said link circuit to said called line for either furnishihg the called subscribers line with ringing current or for transmitting bus signaling current to the calling subscribers line, and means responsive to such connection for disconnecting said operators telephone set from said link circuit.

7. A tele hone system including a calling and a called subscribers line, a link circuit, automatic means for connecting said calling subscribers line to said link circuit,

. tion busy".

8, A telephone system including ca subscribers l e and a calied su. line, link nits,

neeaiae necting said calling subscribers line and an line, a. link circuit, automatic means for connectin said calling subscribers line to said link circuit, means for connecting said link circuit to said called subscribers line, automatic test means for said link circuit for de termining the idle or busy conditionvof said called subscribers line, a supervisory signaling device for said link circuit, and means associated with the link circuit and controlled from a connected station for causing the supervisory signaling device to operate continuously to furnish a disconnect signal and intermittently to furnish a recall signal.

10. A telephone system including a calling subscribers line and a called subscribers line, a link circuit for connectingsaidlines in conversational circuit, automatic test means for said link circuit for either supplying thecalled subscribers line with ringing current or the calling subscribers line with signaling current, and automatic disconnect means for said last circuit operable if the called line is busy and controlled by the calling subscriber for disconnecting said calling line from said link circuit, said disconnect means being ineifective if the called line is idle.

11. A telephone system including a calling subscribers line and a called subscribers line, a link circuit provided with a manual terminal and an automatic switch for use in connecting said lines, automatic test means for said link circuit operable to supply the called subscriberls line with ringing current or the calling subscribers line with busy signalingcurrent dependent uponthe idle or busy condition of the connected called line,

subscriber-controlled means for releasing said automatic means to disconnect saidcall- 111g line from said link clrcuit if said called subscribers line tests busy, and a supervisory the idle or busy condition of the connected called line, and subscriber-controlled means for releasing said automatic means to disconnect said calling line from said link circuit if the called line tests busy, said last 0 means being inefiectiveif said called subscribers line tests idle.

13. A telephone system including a calling 1 and a called subscribers line, a plurality of link circuits, an automatic switch for connecting said calling subscribers line to an idle one of said link circuits, an operators telephone set, means common to said link circuits for rendering all idle ones of said link circuits busy, a relay for said link circuit, for automatically connecting said operators set to said link circuit and for operating said common means, a second relay for said link circuit for disconnecting said operators set from said link circuit and for re- 35 storing saidcommon means, and automatic testing means for said link circuit for either supplying'the called subscriberslinewith ringing current or the calling subscribers line with busy signaling current.

14. A telephone system including a calling and a called subscribers line, a plurality of link circuits, an automatic switch for connecting said calling subscribers line to an idle one of said link circuits, an operators telephone set, means common to said link circuits for rendering all idle ones of said link circuitsbusy, a relay for said link circuit for automatically connecting said operators set to said link circuit and for 7 operating .said common means, a second relay for said link circuit for disconnecting said operators set from said link circuit and for restoring said common means, automatic testing means for said link circuit for either supplying the called subscribers line with ringing current or the calling subscribers line with busy signaling current, and a signal adapted to be intermittently operated if busy signaling current is transmitted to the calling line; i

15. A telephone system including a calling and a called subscribers line, a link circuit provided with a manual terminal, automatic means includin a progressively movable switch for connecting said calling subscribers line to said link circuit, means for said link circuit responsive to such connection for automatically connecting the operators telephone set to said link circuit, manually controlled means for connecting said link circuit to said called subscribers line, means responsive to such connection for automatically disconnecting said operators telephone set from said link circuit, and automatic testing means for said link circuit for either supplying the called subscribers line with ringing current or the calling subscribers line with busy signaling current.

16. A telephone system including a calling and a called subscribers line, a link circuit, for rendering all of the remaining idle link automatic means for connecting said calling circuits at an operators position busy, and subscribers line to said link circuit, means automatic testing means for said link circuit for connecting'said link circuit to said called for either supplying the called subscribers 5 subscribers line, an operators telephone set, line with ringing current or the calling sub- 1 automatic means for connecting and disconscribers line with busy signaling current. necting said operators telephone set and Signed by meat Chicago, county of Cook said link circuit, a group relay for said link and State of Illinois, this 14th day of J anucircuit responsive to the connection of said ary, 1919. p

10 calling telephone line to said link'circuit GEORGEA. YANOCHOWSKI. 

